Roughly 32 million pounds of antibiotics are given to animals that we then consume each year.

It started back in the 1940s, when it became clear that animals given low-dose antibiotics gained weight more quickly. But it’s been in the last 20 years that antibiotic use has really skyrocketed, and recently, some 70% of all antibiotics sold in this country have been for use in food-producing animals. For these animals, low dose antibiotics promote faster growth, treat infections, reduce death rates and improve reproduction.

However, the FDA has several concerns. Does this antibiotic use contribute to the rise of resistant “superbugs?” Just as antibiotics are used to promote weight gain in food animals, might they also be contributing to obesity in humans? Do antibiotics in our food animals affect our intestinal microbiomes? Are antibiotics being overused?

The animals given the highest levels of antibiotics are pigs, then chickens, and then cattle. Notable levels are also found in farmed shrimp and fish. Surprisingly, even organic vegetables may contain antibiotics, because some 75% of antibiotics fed to livestock are excreted into manure that ends up fertilizing our fields.

Do antibiotics given to animals affect our weight? Many types of bacteria in our gut help our body to absorb calories from food. If these bacteria are not in balance, and too many of them break our food down into energy, we may be absorbing more calories from the same amount of food. Interestingly, obese people do indeed have a different mix of gut bacteria than do lean people. In fact, research has shown that transplanting fecal matter of obese mice into thin mice actually does lead to weight gain among the thin mice. However, any data correlating the use of antibiotics to human obesity is very limited.

The science is clear (and it’s more than obvious!) that diet and lifestyle is a factor in obesity, but this does not fully explain our country’s obesity epidemic. We do in fact consume more calories today than in the past. Today’s average daily consumption of 3,900 calories can be compared to 3,400 calories in the early 1900s. Yet while obesity increased very slowly until the middle of the 1970s, it exploded after that.

One large change has been the ever-increasing levels of antibiotics in our food and water. Our obesity epidemic may in fact be partly due to “super size me” trends, partly due to consuming antibiotics that affect calorie absorption, and partly due to other factors. Clearly, more research is needed.

What is the solution? Right now in the United States, the FDA has asked the food industry to voluntarily phase out antibiotic use. If you’re concerned about this, look for organic meat from animals that have been raised without the use of antibiotics. The demand for these food products has increased drastically over the past few years. The food labels will read: “No Antibiotics”, or “Raised Without Antibiotics”.

Choose restaurants that have pledged not to use meat or seafood with antibiotics. Shop at markets (like Whole Foods) that are committed to selling meat with no antibiotics. Costco has tightened its standards for the use of antibiotics in the meat and poultry it sells. You may choose to look for other sources of protein and adopt a plant-based diet.

Until more studies are conducted, we simply cannot be certain whether eating antibiotic-treated foods are bad for us.

Dr. Alan Frischer is former chief of staff and former chief of medicine at Downey Regional Medical Center. Write to him in care of this newspaper at 8301 E. Florence Ave., Suite 100, Downey, CA 90240.